Hydra

The Lernaen Hydra depicted in a Roman
mosaic
(c. 2nd AD)

A fabulous monster of the ancient world, said to have inhabited the marshes
of Lernaea, in Argolis, not far from the sea-coast. Accounts vary both as
to its origin and appearance. Some make it the issue of Styx and the Titan
Pallas, and others, of Echidna and Typhon. It is represented as having several
heads, which immediately grew up again as often as they were cut off. The
number generally ranged from seven to nine, though Simonides gives it fifty,
and some historians a hundred, and even more. Its mouth, which were as numerous
as its heads, discharged a subtle and deadly venom. The destruction of this
reptile was one of the twelve labors of Hercules.